import type { UsageLedger } from "./usage-ledger.js";
export interface UsageCacheOptions {
    /** How long a window's total may be reused. Default 2 000 ms. */
    ttlMs?: number;
    /**
     * Cap on remembered windows. Beyond it the expired entries are dropped, and if
     * that is not enough the cache is cleared outright.
     *
     * A bound is needed because the key includes the window, so a long-running
     * process accumulates one entry per window per caller for ever. Clearing is
     * safe — the next read simply goes to the ledger — whereas an unbounded map is
     * a slow leak that only shows up in production.
     */
    maxEntries?: number;
}
/**
 * Wrap a ledger so repeated reads of the same window inside `ttlMs` cost one
 * request instead of one per call.
 *
 * ```ts
 * const ledger = cachedUsageLedger(
 *   stripeUsageLedger({ perCaller: stripeScopeUsageLedger() }),
 *   { ttlMs: 2_000 },
 * );
 * ```
 *
 * `covers` is inherited unchanged: caching does not alter WHICH windows the
 * underlying ledger can see, only how often it is asked.
 */
export declare function cachedUsageLedger(inner: UsageLedger, opts?: UsageCacheOptions): UsageLedger;
//# sourceMappingURL=usage-cache.d.ts.map